Skin prickers

ABSTRACT

A skin pricker has an elongate housing containing a spring-loaded lancet which, when released from a rearward, cocked position by a trigger, shoots forward momentarily to project the tip of its needle through one end of the housing. The lancet is then prevented by a spring ratchet from being returned again to the cocked position. The cocking can be done through a twist-and-pull cap initially covering the needle tip and extending through that one end of the housing, the user pushing the cap to retract the lancet from its initial position. To guard against the lancet being prematurely pulled forwards by the cap and being trapped against cocking by the ratchet, the lancet has a formation that will engage a part of the trigger.

[0001] This invention relates to skin prickers. It is concerned withskin prickers of the kind where a lancet is pushed back in its housingto a cocked position by its needle cap, which can then be removed by atwist and pull action, leaving the lancet ready to use. When fired, theneedle tip momentarily projects and the bounce-back of the lancetwithdraws it into the housing. Arrangements are made to prevent thelancet being pushed right back again, for example using the discardedcap, to the cocked position. So it is a single use device and has to bediscarded.

[0002] A convenient way of preventing such re-use is a spring ratchetmechanism. When assembled, the lancet is in an intermediate positionwith the ratchet ineffective against the rearward movement to the cockedposition. But after firing, the lancet goes forward beyond its assembledposition, and this allows a pawl to click past a tooth before the needletip projects. The lancet is thus not prevented from bouncing backsufficiently to retract the needle tip, but it is arrested by theratchet mechanism if any attempt is made to re-cock it.

[0003] There is a problem with this since a careless user can quiteeasily and accidentally pull the needle cap before the device is cocked.This can draw the lancet forward so that the ratchet mechanism engages.There is therefore an un-used pricker with the lancet trapped and unableto be cocked.

[0004] It is the aim of this invention to prevent that accidentalmis-use.

[0005] According to the present invention there is provided a skinpricker comprising an elongate housing, a lancet within the housing,spring urged towards the forward end thereof momentarily to project itsneedle tip through an aperture at said forward end when the lancet isreleased from a cocked position, and a trigger carried by the housingwith two modes of engagement with the lancet, in the first moderestraining the lancet from significant forward movement from itsinitial position but allowing retraction of the lancet to the cockedposition, and in the second mode holding the lancet in said cockedposition until operation of the trigger releases it.

[0006] Conveniently, the lancet has a ratchet type engagement with thetrigger, snapping back past a tooth on the trigger as it reaches thecocked position. That tooth on the trigger can also be employed as thefirst mode restraint, co-operating with a projection on the lancet tostop the latter moving forwards. But when the trigger is operated tofire the lancet, its tooth will be lifted clear of the lancet, and willnot obstruct that projection as it moves forward.

[0007] In the preferred form, a removable needle cap initially shroudsthe needle tip and extends through the aperture. It can also serve asmeans by which the lancet can be pushed back from its initial positionto the cocked position.

[0008] There will generally be means for ensuring that the lancet cannotbe re-cocked after cocking and release, and this conveniently is aratchet arrangement between the lancet and housing. In one form thelancet may have a spring finger pointing rearwardly and the housing willthen have a tooth with which it co-operates. In the initial position ofthe lancet, the finger will lie against the tip of the tooth and as thelancet is pushed rearwardly, the finger will slide over that tip. Whenthe lancet is fired, the rear end of the finger will go forward beyondthe tooth before the needle tip projects and will be sprung to aposition to abut the tooth as the lancet bounces back again retractingthe needle tip. The lancet will thus be arrested and prevented fromreturning to the cocked position.

[0009] Preferably, there will be a symmetrical arrangement, with twofingers on opposite sides of the lancet co-operating with opposed teethwithin the housing. This will ease assembly as the lancet can be placedin either one of two ways.

[0010] It would be possible to reverse the arrangement and haveforwardly extending fingers on the housing and teeth on the lancet.

[0011] For a better understanding of the invention, one embodiment willnow be described, by way of example, with reference to the accompanyingdrawings, in which:

[0012]FIG. 1 is a plan view of a skin pricker in its assembledcondition, but before closure of its housing,

[0013]FIG. 2 is a section on the line II-II of FIG. 1,

[0014]FIG. 3 is a plan view of the pricker in its cocked condition, thehousing being shown open,

[0015]FIG. 4 is a section on the line IV-IV of FIG. 3, and

[0016]FIG. 5 shows three views of the lancet of the pricker.

[0017] The pricker has an elongate box-like housing 1 in twocomplementary halves 2 and 3 hinged together by an integral thin web 4along one of the longitudinal sides. It houses a a lancet 5 which has amoulded plastics body encasing a needle 6 whose tip is initiallyshrouded by an elongate cap 7. There are cut-outs 8 at the forward endsof the halves 2 and 3 which combine to create an aperture through whichthe cap 7 can freely move, and through which the needle tip momentarilyprojects when the device is fired. The lancet is urged forwardly by ahelical spring (not shown) acting between its rear end and the end ofthe housing 1 opposite the aperture 8. The firing of the lancet is bypressing the rear end of a trigger 9 integrally moulded with the half 2,this being of the rocker type and having a tooth 10 projecting into thehousing at its forward end.

[0018] The half 2 also has two opposed teeth 11 on its side walls eachwith a shallow slope to the rear and a slight undercut on the forwardside.

[0019] The lancet 5 has a spine 12 encasing most of the needle 6. Atabout its mid-length it is expanded into an arrow-head-like formation 13pointing rearwardly. Forward of this there are wings 14 making arectangular plate-like structure, at whose transverse forward edge thereis another formation 15 of arrowhead section pointing rearwardly. Fromthe outer rear corners of the wings 14 there extend rearwardly fingers16 which turn outwardly at their tips 17. At the rear end of the spine12 there is a mushroom head 18 which locates the forward end of thehelical spring. The lancet is generally symmetrical apart from minorfeatures introduced for tooling reasons so that it does not matter whichway up it is assembled into the housing, as shown in FIGS. 1 and 2. Thetips 17 of the fingers 16 then lie just behind the teeth 11, and thetooth 10 of the trigger is just in front of the formation 13.

[0020] Supposing a user tries to remove the cap 7, with a twist and pullaction he might shift the lancet 5 marginally forwards, but thismovement will be arrested by the formation 13 engaging the tooth 10. Thetips 17 will not override the teeth 11. Therefore, although the cap 7may have come free, the pricker is not rendered useless and there is noproblem in re-inserting the cap and pushing back the lancet. Normally,of course, the user will push back before attempting to remove the cap7.

[0021] As the lancet 5 moves rearwardly, the fingers 16 simply slideover the tips of the teeth 11. But as the formation 15 reaches the tooth10, the co-operating wedge-like surfaces tilt the trigger, which snapsover the formation 15 to hold the lancet in the rear, cocked position asshown in FIGS. 3 and 4. Then the cap 7 will be finally removed, thepricker applied to the skin and the trigger 9 pressed to release thelancet.

[0022] On firing, the lancet shoots forward beyond its assembledposition of FIGS. 1 and 2, so that the fingers 16 flex inwardly as thetips 17 snap over the teeth 11. This happens just before the needle tipprojects. The tooth 10 is held clear of the formation 13 and so does notimpede the final part of the lancet's travel. After the tip projects,the lancet bounces back, but can go only a short distance, beingarrested by the outwardly sprung tips 17 abutting by the teeth 11. Thusthe pricker is non-re-usable.

1. A skin pricker comprising an elongate housing, a lancet within thehousing, spring urged towards the forward end thereof, momentarily toproject its needle tip through an aperture at said forward end when thelancet is released from a cocked position, and a trigger carried by thehousing with two modes of engagement with the lancet, in the first moderestraining the lancet from significant forward movement from itsinitial position but allowing retraction of the lancet to the cockedposition, and in the second mode holding the lancet in said cockedposition until operation of the trigger releases it.
 2. A skin prickeras claimed in claim 1, wherein the lancet has a ratchet type engagementwith the trigger, snapping back past a tooth on the trigger as itreaches the cocked position.
 3. A skin pricker as claimed in claim 2,wherein said tooth also serves as the first mode restraint, co-operatingwith a projection on the lancet to stop the lancet moving forwards but,when the trigger is operated to fire the lancet, being lifted clear ofthe lancet so as not to obstruct said projection as the lancet movesforward.
 4. A skin pricker as claimed in claim 1, 2 or 3, wherein aremovable needle cap initially shrouds the needle tip and extendsthrough the aperture, and also serves as means by which the lancet canbe pushed back from its initial position to the cocked position.
 5. Askin pricker as claimed in any preceding claim, and including means forensuring that the lancet cannot be re-cocked after cocking and release.6. A skin pricker as claimed in claim 5, wherein the means for ensuringthat the lancet is not re-cocked is a ratchet arrangement between thelancet and housing.
 7. A skin pricker as claimed in claim 6, wherein thelancet has a spring finger pointing rearwardly and the housing has atooth with which it co-operates, the arrangement being such that, in theinitial position of the lancet, the finger lies against the tip of thetooth and as the lancet is pushed rearwardly, the finger slides overthat tip, and such that when the lancet is fired, the rear end of thefinger goes forward beyond the tooth before the needle tip projects andis sprung to a position to abut the tooth as the lancet bounces backagain retracting the needle tip.
 8. A skin pricker as claimed in claim7, wherein there is a symmetrical arrangement, with two fingers onopposite sides of the lancet co-operating with opposed teeth within thehousing.
 9. A skin pricker as claimed in claim 7 or 8, wherein the toothand finger arrangement is reversed, there being at least one forwardlyextending finger on the housing and an associated tooth on the lancet.